A method for calculating and evaluating gear knock for balanced shaft scissors teeth

Abstract

This invention discloses a method for calculating and evaluating gear knocking on balance shaft scissor teeth, comprising the following steps: constructing a rigid model of an engine balance shaft system; performing mesh generation to obtain a finite element model; setting condensed nodes on the finite element model and coupling the condensed nodes with the contact boundaries; performing condensation processing on the finite element model and using the generated condensed model to replace the finite element model for mechanical analysis; making the gears flexible; applying excitations at various speeds on the crankshaft and starting simulation calculations; extracting the meshing force on the tooth surface of each gear pair at each speed; processing the meshing force data to obtain the peak meshing force, obtaining the impact index based on the peak meshing force, and obtaining the knocking evaluation based on the impact index. The method described in this invention can establish a fully flexible balance shaft system simulation model and quantitatively evaluate the knocking noise of balance shaft scissor teeth, providing a basis for the analysis and optimization of gear knocking problems on balance shaft scissor teeth.

Description

Technical Field

[0001] This invention belongs to the field of NVH (Noise, Vibration, and Harshness) in automotive engines, and particularly relates to a method for calculating and evaluating gear knocking on balance shaft scissor teeth. Background Technology

[0002] With the continuous development of the automotive industry and the upgrading of consumption, people have increasingly higher requirements for the comfort of automobiles, making engine vibration and noise levels one of the important evaluation indicators for the overall performance of engines and automobiles. Reciprocating engines generate rotational and reciprocating inertial forces due to the periodicity of their working process and the periodicity of their component movements. For inline four-cylinder engines, the second-order reciprocating inertial force cannot be balanced by the engine itself. In engineering, balance shafts with scissor teeth are often used to balance the second-order reciprocating inertial force of the engine, but this can cause noise problems such as gear squeal and gear knocking. Most research on the abnormal noise of balance shaft scissor teeth focuses on gear squeal, and due to the special structure of scissor teeth and the complexity of the gear knocking mechanism, a unified evaluation method for the gear knocking abnormal noise problem of scissor teeth has not yet been established.

[0003] Currently, the evaluation of gear knocking mainly includes speed fluctuation evaluation index, speed standard deviation evaluation index, energy evaluation index, impulse evaluation index, and Jerk evaluation index. Among them, speed fluctuation and speed standard deviation evaluation indexes are suitable for qualitative analysis of gear knocking, but their accuracy has a certain error. Energy index and impulse index are more accurate and widely used for evaluating the knocking of general unloaded gears. However, due to the torsion spring effect of scissor teeth, there is a pre-torque between meshing gears, which causes energy loss not only to be generated by knocking, but also by tooth surface friction and gear squealing. Therefore, when energy index or impulse index is applied to scissor teeth, it will produce a large error, and may even be completely inconsistent with the test results. In 2013, researchers such as Yogesh Bile proposed the Jerk knocking evaluation index in the SAE (Society of Automotive Engineers) journal. This evaluation index can evaluate gear knocking noise better. However, this evaluation index still has the following shortcomings: (1) it uses the root mean square method for knocking evaluation within a certain time period; (2) it calculates all collected gear meshing forces indiscriminately. At different rotational speeds, the number of times a gear strikes within the same cycle varies. The root mean square (RMS) only reflects the average intensity of each strike, not the total intensity of the strikes within the same cycle. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating and evaluating gear knocking in balance shaft scissor gears. This method involves fully flexible modeling of the balance shaft system, obtaining the meshing force on the tooth surfaces of each gear pair based on the simulation model, and processing this meshing force to obtain impact indices for evaluating scissor gear knocking. These impact indices can then be used to quantitatively evaluate the abnormal knocking noise of balance shaft scissor gears, analyze the degree of gear knocking at different speeds in the balance shaft system, and provide a basis for the analysis and optimization of gear knocking problems in balance shaft scissor gears.

[0005] To achieve the objective of this invention, the present invention provides a method for calculating and evaluating gear knocking on balance shaft scissor teeth, comprising the following steps:

[0006] (1) Build a rigid model of the engine balance shaft system and set boundary conditions;

[0007] (2) Mesh the components of the rigid model of the engine balance shaft system, excluding gears and bearings, to obtain the finite element model;

[0008] (3) Set up condensation nodes on the finite element model and couple the condensation nodes to the contact boundary;

[0009] (4) Import the finite element model of the generated condensed node into the transmission system analysis software, perform finite element replacement according to the connection relationship, and complete the condensation process of the finite element model in the software. Use the generated condensed model to replace the finite element model for mechanical analysis.

[0010] (5) Make the gears more flexible;

[0011] (6) Apply various speed excitations to the crankshaft and start the simulation calculation;

[0012] (7) Extract the tooth surface meshing force of each gear pair at each speed from the simulation calculation results;

[0013] (8) Data processing of the meshing force is performed to obtain the peak meshing force. Based on the peak meshing force, the impact index is obtained, and based on the impact index, the knocking evaluation is obtained, wherein:

[0014] Impact indicators are I driven It is the moment of inertia of the driven gear. It is all the three working cycles of the engine at a certain speed. The cumulative value, It is the derivative of the peak meshing force with respect to time;

[0015] The tapping rating is RI n This represents the knocking evaluation that occurs between the nth pair of meshing gears.

[0016] Furthermore, in step (1), the actual connection point between the engine block and the suspension bracket is used as the boundary condition.

[0017] Furthermore, in step (2), when performing mesh generation, the second-order tetrahedral element is selected as the mesh type, taking into account the size of the computational scale.

[0018] Furthermore, in step (3), condensed nodes are set on the finite element model according to the connection relationship between the parts.

[0019] Furthermore, in step (4), the mechanical analysis is performed using a condensation model, which can significantly reduce the number of degrees of freedom of the model itself and improve the computational efficiency of the mechanical analysis.

[0020] Furthermore, in step (5), since the gear modeling of the transmission system analysis software is relatively accurate and the gear size is small, the gear can be accurately modeled and made flexible directly in the software, and finally the full flexibility of the engine balance shaft system is completed.

[0021] Furthermore, the established engine balance shaft system model includes the engine block, crankshaft, balance shaft tray, balance shaft, crankshaft gear, scissor gear, driven gear, and bearings. The complete scissor gear consists of scissor main teeth, scissor secondary teeth, torsion spring, snap ring, and pin.

[0022] Furthermore, the assembly relationship of the scissor gear is as follows: the main scissor gear is fixed on the balance shaft by an interference fit, the auxiliary scissor gear floats on the hub of the main scissor gear, and is axially limited by a snap ring. The main and auxiliary gears generate a preload torque when they rotate relative to each other through the middle pin and torsion spring, which will cause the main and auxiliary scissor gears to contact the left and right tooth surfaces of the crankshaft gear respectively, thereby eliminating the tooth backlash.

[0023] Furthermore, in order to represent the force conditions between contacting components in the software, axial or radial clearance bearings are set at the corresponding contact positions for force transmission.

[0024] Furthermore, the data processing of the meshing force in step (8) includes the following steps:

[0025] (a) Screening of meshing force data: When the tooth surfaces disengage and then re-engage, an impact is considered to have occurred. Therefore, it should be determined whether the meshing force starts from 0 kN each time. According to the steel-on-steel impact test, the minimum impact time is 0.5 ms. Therefore, it should be determined whether the impact time of each time is greater than 0.5 ms. If the above requirements are not met, the data should be discarded.

[0026] (b) The peak value of the meshing force and its corresponding time for each impact are identified by the program, and the derivative of the peak meshing force with respect to time is obtained.

[0027] (c) All three working cycles of the engine at a certain speed By summing, we get

[0028] (d) Calculate the impact index;

[0029] (e) Calculate the impact evaluation of the entire balance shaft system;

[0030] (f) The data processing procedure for tooth surface meshing force at other speeds is repeated from (a) to (e) to obtain the knocking evaluation results at other speeds;

[0031] Furthermore, the subjective evaluation of the experiment identifies the rotational speed at which obvious gear knocking begins, and the impact index at that speed is used as the knocking threshold for this model.

[0032] Compared with existing technologies, the beneficial effects of the present invention are at least as follows:

[0033] (1) Establishing a fully flexible balance shaft system model can more accurately represent the deformation of each component in the system and improve the accuracy of the simulation;

[0034] (2) The impact index based on the meshing force of the tooth surface can avoid the influence of the pre-torque of the scissor teeth and improve the accuracy of the evaluation results.

[0035] (3) The impact index based on the meshing force of the tooth surface can quantitatively evaluate the knocking level at different speeds. The evaluation process is simple and the results are intuitive.

[0036] (4) By combining the subjective evaluation of bench tests with the knocking index, the knocking threshold of the model can be determined.

[0037] (5) The impact index based on the meshing force of the tooth surface is accurate and reliable, and can provide a basis for the analysis and optimization of the gear knocking problem of the balance shaft scissor teeth. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the calculation process provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the scissor tooth structure according to an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the creation of a flexible node ring in a gear according to an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the speed excitation curve at 3000 rpm in an embodiment of the present invention;

[0042] Figure 5 This refers to the meshing force on the left tooth surface of the crankshaft gear and the scissor main gear at 3000 rpm in this embodiment of the invention.

[0043] Figure 6 This is a schematic diagram of the process for data processing of meshing force in an embodiment of the present invention;

[0044] Figure 7 This is an enlarged schematic diagram of a certain meshing force data in an embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram of the impact evaluation results at various rotational speeds according to an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative and explanatory purposes only and are not intended to limit the invention. Any modifications and / or alterations made to this invention will fall within the scope of protection of this invention.

[0047] like Figure 1 As shown, the present invention provides a method for calculating and evaluating gear knocking on balance shaft scissor teeth, comprising the following steps:

[0048] Step 1: Use a professional transmission system analysis software to build a rigid model of the engine balance shaft system, and use the actual connection between the engine block and the suspension bracket as the boundary condition.

[0049] In some embodiments of the present invention, a rigid model of the engine balance shaft system is built using the professional transmission system analysis software MASTA. The established engine balance shaft system model includes the engine block, crankshaft, balance shaft tray, balance shaft, crankshaft gear, scissor gear, driven gear, and bearings. The scissor gear includes scissor main teeth, scissor secondary teeth, torsion spring, snap ring, and pin. Figure 2 As shown. The main scissor gear is fixed to the balance shaft by an interference fit, while the auxiliary scissor gear floats on the hub of the main scissor gear. Axial positioning is achieved by a snap ring. The main and auxiliary gears generate a preload torque when they rotate relative to each other via a central pin and a torsion spring. This causes the main and auxiliary scissor gears to contact the left and right tooth surfaces of the crankshaft gear, respectively, thereby eliminating tooth backlash.

[0050] In some embodiments of the present invention, during the specific modeling process, since the main components need to be replaced by finite element analysis later, fuzzy modeling can be used, that is, ignoring the non-critical dimensions of parts such as crankshaft, balance shaft, and gear spokes, and only retaining the critical dimensions that have assembly relationships with other parts.

[0051] In the software, to represent the force conditions between contacting components, axial or radial clearance bearings are installed at the corresponding contact positions for force transmission. In some embodiments of the present invention, based on actual bench tests, the simulation model uses three actual connection points between the engine block and the suspension bracket as boundary conditions.

[0052] Step 2: Import the components other than gears and bearings from the rigid model of the engine balance shaft system into the finite element mesh generation software to generate a finite element model.

[0053] In some embodiments of this invention, second-order tetrahedral elements are selected as the mesh type to consider the computational scale during mesh generation. Small parts such as balance shafts and gear spokes can use a 4mm mesh size, while large parts such as engine blocks, crankshafts, and balance shaft trays can use a 6mm-8mm mesh size. The mesh is further refined at the contact points between parts to improve analysis accuracy. Based on engineering experience, the mesh size for engine blocks is typically around 1 million, while the mesh size for crankshafts, balance shaft trays, and balance shafts is approximately 300,000-500,000. This approach ensures both analytical accuracy and good solution speed.

[0054] Step 3: Before the finite element replacement, based on the connection relationship between each part, set condensation nodes on the finite element model and couple the condensation nodes to the contact boundary.

[0055] In some embodiments of the present invention, according to the actual contact relationship, the condensation node is set at the point where the mid-surface of the contact surface intersects with the rotation axis of the part, and the condensation node is coupled to the actual contact surface using Rbe3.

[0056] Step 4: Import the generated condensed node finite element model into the transmission system analysis software, perform finite element replacement according to the connection relationship, and complete the condensation processing of the finite element model in the software. Use the generated condensed model to replace the finite element model for mechanical analysis.

[0057] In some embodiments of the present invention, during finite element replacement, the finite element model is first aligned, then the condensed nodes of different parts at the same location are coupled together, and then a condensation process is performed. After condensation, a corresponding condensed mass matrix and condensed stiffness matrix are generated. The generated condensed model is then used to replace the finite element model for mechanical analysis. Using a condensed model for mechanical analysis can significantly reduce the number of degrees of freedom of the model itself, which is beneficial to improving the computational efficiency of mechanical analysis.

[0058] Step 5: Make the gears more flexible.

[0059] Because the gear modeling of this transmission system analysis software is quite accurate and the gear size is small, precise gear modeling and flexibility can be performed directly in the software, ultimately completing the full flexibility of the engine balance shaft system.

[0060] In some embodiments of the present invention, the gear can be divided into two parts, a hub and a gear ring, in the software. When the hub connects to the gear ring, a cohesive node can be automatically created in the software. The connection method is to create a flexible node ring, that is, to uniformly generate corresponding nodes on the circumference and couple them with the mesh of each region, such as... Figure 3 As shown. The gear ring can be generated as a full 3D finite element model in the Advanced LTCA module, which ensures accurate calculation of TE (Transmission error) and tooth root stress.

[0061] Step 6: Apply various speed excitations to the crankshaft, set the lubricating oil, and perform simulation calculations.

[0062] In some embodiments of the present invention, the actual operating speed range of the engine is divided into equally spaced speeds of 500 rpm according to experimental conditions, and the different speeds measured in the experiment are applied to the crankshaft as inputs. A schematic diagram of the speed excitation curve at 3000 rpm is shown below. Figure 4 As shown. The lubricating oil used is the 0w / 5w grade under the SAE standard. The oil temperature is set to be consistent with the oil temperature of the bench test, and the simulation calculation begins.

[0063] Step 7: Obtain the meshing force of each gear pair at each speed from the simulation calculation results.

[0064] In some embodiments of the present invention, the meshing forces on the left and right tooth surfaces of the four gears—crankshaft gear, scissor main gear, scissor secondary gear, and driven gear—can be obtained from simulation calculation results. The meshing force on the left tooth surface of the crankshaft gear and the scissor main gear at 3000 rpm is shown below. Figure 5 As shown.

[0065] Step 8: Process the meshing force data through the program.

[0066] This section describes how to process meshing force data using Matlab programming, with the specific programming approach as follows: Figure 6 As shown. The program processes meshing force data through the following steps:

[0067] (a) First, read the meshing force data of the left and right tooth surfaces of the four gears at a certain speed from the Excel file;

[0068] (b) Identify the meshing force data length as a boundary condition, because an error will occur if the data is read out of bounds;

[0069] (c) A knocking occurs only when the tooth surfaces disengage from the mesh and then re-engage. Therefore, it should be determined whether the meshing force starts from 0 kN and whether the meshing force is greater than 0 kN. If not, the data should be skipped.

[0070] (d) According to the steel-on-steel impact experiment, the minimum impact time is 0.5 ms. Therefore, it is necessary to determine whether the duration of each impact is greater than 0.5 ms. If not, skip that data segment. Filter the meshing force data. According to the impact hammer experiment, the shortest contact time of steel-on-steel impact is 0.5 ms. Therefore, if the duration of each impact force is less than 0.5 ms, discard that impact data.

[0071] (e) Identify the peak value of the meshing force and its corresponding time for each tapping action through the program, because the meshing force does not have only one peak value during each tapping action, such as... Figure 7 As shown, the peak meshing force cannot be found directly by using an incremental judgment method. During the program identification process, minute fluctuations need to be skipped. In some embodiments of this invention, the nth data point is compared sequentially with the (n+1), (n+2), ..., (n+20)th data points. If all subsequent 20 data points are smaller than the nth data point, then the nth data point is considered the peak value.

[0072] (f) Differentiate the peak meshing force with respect to time to obtain It is the derivative of the peak meshing force with respect to time (i.e. Where F peak t is the peak value of the meshing force (where t is time). Because the greater the change in meshing force in a short time, the more obvious the knocking sound of the gears will be. According to the principle of sound generation, only the rising edge of the knocking force is important. Therefore, we only consider the derivative of the peak value of the meshing force with respect to time. Moreover, we use the derivative of the tooth surface meshing force with respect to time to evaluate the knocking level, which can effectively avoid the influence of the pre-torque of the scissor teeth.

[0073] (g) All three working cycles of the engine at a certain speed By accumulating, we can obtain Multiple knocking events occur during the engine's three working cycles, so the total knocking noise generated during this time period needs to be accumulated to reflect the total knocking noise generated during that time.

[0074] (h) The definition of the impact index is... Where I driven It is the moment of inertia of the driven gear;

[0075] (i) The knocking evaluation of the entire balance shaft system is: RI is a collective symbol, an abbreviation for Rattle Index. RI1 represents the rattle assessment between the first pair of meshing gears, RI2, RI3, and RI4 represent the rattle assessment. nSimilarly, the formula in step (h) is used to calculate the results, except that the subscript Jerk in the formula in step (h) is replaced with a specific pair of meshing gears.

[0076] (j) Determine if all speeds have been traversed. If not, read the meshing force data at other speeds and repeat the process, i.e., repeat (a)-(i). This can yield the impact evaluation results for all speeds, such as... Figure 8 As shown.

[0077] The knocking evaluation values ​​at various speeds are obtained through this calculation and evaluation method. Combined with the subjective evaluation of the experiment, the speed at which obvious gear knocking begins is identified. The evaluation value corresponding to that speed is used as the knocking threshold of this model. Therefore, in subsequent simulation calculations, as long as the knocking rating value is higher than this threshold, gear knocking is considered to have occurred.

[0078] This invention establishes a fully flexible balance shaft system model, which can accurately represent the deformation of each component in the system and improve the accuracy of the simulation. This evaluation method, combined with the structural characteristics of scissor teeth, proposes an evaluation method for impact indices from the perspective of tooth surface meshing force, avoiding the problem of pre-torque in scissor teeth. The method described in this invention can establish a fully flexible balance shaft system simulation model and quantitatively evaluate the knocking noise of balance shaft scissor teeth, providing a basis for the analysis and optimization of gear knocking problems in balance shaft scissor teeth.

[0079] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating and evaluating gear knocking on balance shaft scissor teeth, characterized in that, Includes the following steps: (1) Build a rigid model of the engine balance shaft system and set boundary conditions; (2) Mesh the components of the rigid model of the engine balance shaft system, excluding gears and bearings, to obtain the finite element model; (3) Set up condensation nodes on the finite element model and couple the condensation nodes to the contact boundary; (4) Import the finite element model of the generated condensed node into the transmission system analysis software, perform finite element replacement according to the connection relationship, and complete the condensation process of the finite element model in the software. Use the generated condensed model to replace the finite element model for mechanical analysis. (5) Make the gears more flexible; (6) Apply various speed excitations to the crankshaft and start the simulation calculation; (7) Extract the tooth surface meshing force of each gear pair at each speed from the simulation calculation results; (8) The meshing force is processed to obtain the peak meshing force. Based on the peak meshing force, the impact index is obtained, and based on the impact index, the knocking evaluation is obtained, wherein: Impact indicators are I driven It is the moment of inertia of the driven gear. It is all the three working cycles of the engine at a certain speed. The cumulative value, It is the derivative of the peak meshing force with respect to time; the knocking evaluation is... RI n This represents the knocking evaluation that occurs between the nth pair of meshing gears.

2. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, The established engine balance shaft system model includes the engine block, crankshaft, balance shaft tray, balance shaft, crankshaft gear, scissor gear, driven gear, and bearings. The scissor gear includes scissor main teeth, scissor secondary teeth, torsion spring, snap ring, and pin.

3. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 2, characterized in that, The assembly relationship of the scissor gear is as follows: the main scissor gear is fixed on the balance shaft by interference fit, the auxiliary scissor gear floats on the hub of the main scissor gear, and the axial movement is limited by a snap ring. The main and auxiliary gears generate a preload torque when they rotate relative to each other through the middle pin and torsion spring, which will cause the main and auxiliary scissor gears to contact the left and right tooth surfaces of the crankshaft gear respectively, thereby eliminating the tooth backlash.

4. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, In order to represent the force between contacting components in the software, axial or radial clearance bearings are set at the corresponding contact positions for force transmission.

5. In the calculation and evaluation method for gear knocking of balance shaft scissor teeth according to claim 1, in step (2), the mesh type is selected as second-order tetrahedral element.

6. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, In step (3), the condensation node is set at the point where the middle surface of the contact surface intersects with the rotation axis of the part, and the condensation node is coupled to the actual contact surface using Rbe3.

7. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, In step (4), during finite element replacement, the finite element model is first aligned, and then the condensation nodes of different parts at the same position are coupled together and then condensation processing is performed.

8. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, In step (5), the gear is divided into two parts: the hub and the gear ring. When the hub is connected to the gear ring, the software automatically creates a cohesive node. The connection method is to create a flexible node ring, which means that the corresponding nodes will be generated evenly on the circumference and coupled with the mesh of each region.

9. The method for calculating and evaluating gear knocking on balance shaft scissor teeth according to claim 1, characterized in that, In step (8), the data processing of the meshing force includes the following steps: (a) Screening of meshing force data: When the tooth surface disengages from meshing, it is only considered to be an impact when it re-contacts. Therefore, it should be determined whether the meshing force starts from 0kN for each time; and whether the time of each impact is greater than the minimum impact time. If the above requirements are not met, the data should be discarded. (b) Identify the peak value of the meshing force for each impact and its corresponding time, and obtain the derivative of the peak meshing force with respect to time. (c) All three working cycles of the engine at a certain speed By summing, we get (d) Calculate the impact index; (e) Calculate the impact evaluation of the entire balance shaft system; (f) Repeat (a) to (e) the data processing procedure for tooth surface meshing force at other speeds to obtain the knocking evaluation results at other speeds.

10. A method for calculating and evaluating gear knocking on balance shaft scissor teeth according to any one of claims 1-9, characterized in that, By obtaining the knocking evaluation values ​​at each speed through step (8), and combining the subjective evaluation of the experiment to identify from which speed obvious gear knocking begins, the evaluation value corresponding to that speed is used as the knocking threshold of this model. Therefore, in the subsequent simulation calculation, as long as the knocking rating value is higher than this threshold, it is considered that gear knocking has occurred.

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